Islington murder of cyclist Alan Cartwright, 15, caught on CCTV
Police have released CCTV footage of the moment a 15-year-old boy was fatally stabbed while cycling in a north London street.
Alan Cartwright was attacked near Copenhagen Street, in Islington, last Friday, while out with two friends.
He managed to cycle away but collapsed on nearby Caledonian Road and was pronounced dead at the scene.
His mother said the footage looks like he got punched, yet two minutes later he collapsed and died.
Michelle Watson, 39, added: "I feel angry, I want somebody found for this. I just feel numb."
The video shows Alan and his two friends being attacked and pushed off their bikes by three youths.
Det Ch Insp Chris Jones said: "The footage of the suspects attacking Alan and his friends is truly shocking.
"Alan stood no chance of defending himself against his attacker who casually stepped out in front of him and stabbed him in the chest.
"Identifying and arresting the suspects is our absolute priority."
After Alan's two friends were pushed off, the suspects - initially described as men in the hours after the killing - rode off on their bicycles.
His 21-year-old sister, Cherrie Smith, said: "We want any witnesses to give as much information as they possibly can. If you have a little brother or sister, ask yourself 'what if it was them?'
"If that was me, I wouldn't be able to live with myself.
"People are saying 'wrong place, wrong time', but those people shouldn't be carrying knives on them."
She added: "He has always put a front on in front of me and his friends that he was like a hard man, but he wouldn't hurt a fly, he really wouldn't.
"I hope someone gets found for this. Knowing he has been taken away from us in such an unlawful way, it's just heartbreaking because there's a chance someone could get away with this."
A post-mortem examination confirmed the cause of Alan's death as a single stab wound to the chest.
Det Ch Insp Jones added: "I would like to re-appeal to anyone who may know something about Alan's murder and the robbery of the bikes.
"Where are the two bicycles that were taken? Someone may have noticed a new bike brought home or perhaps you have been offered a similar bike for sale?
"If so, I would urge you to contact the police."
Former EastEnders actress and anti-knife campaigner Brooke Kinsella described the killing as "cowardly and senseless".
Ms Kinsella, whose brother Ben was fatally stabbed 11 times in 2008 as he fled a fight in Islington, tweeted on Saturday: "Another young boy lost to knife crime, another family destroyed. Sickening, cowardly, senseless culture.
"Heart is weary #PutDownYourKnives".